Consumer unit upgrades is worth doing properly once rather than cheaply twice. That context is what stops "estimate" turning into "extra". There is a version of this job that is quick and a version that is not, and the difference is almost always every CU job is Part P notifiable. A short survey tells us which one your property is. We would rather rule out every CU job is Part early than discover it late.
The paperwork for consumer unit upgrades is only useful if it reflects what is actually installed, which is why circuits get identified rather than assumed. Most Neath visits settle this within the first hour. Here is how consumer unit upgrades works in practice for a property in Neath, start to finish.




